1. Field of the Invention
The present invention relates to medical instruments and, in particular, to a trocar/cannula combination with built-in safety mechanisms which maintain an air-tight seal when the surgeon passes surgical instruments through it.
Trocars are typically sharp pointed surgical instruments used to puncture a body cavity and are designed to be used with a cannula in the form of an outer sleeve which after the trocar is removed, permits the insertion of surgical instruments to allow a surgeon to perform various procedures without the necessity of leaving the body cavity open. Thus, the trocar creates a passageway through a body wall in order that the surgeon may gain access to an interior portion of the body. Once the body cavity has been punctured by the trocar, the sharp trocar is removed from the cannula thereby leaving the cannula extending into the body cavity. Surgical procedures may then be performed through the cannula with accessory instrumentation such as laparoscopes, endoscopes, dissectors, graspers and similar type instruments.
Trocars provide a means for penetrating tissue and muscle. The prior art trocars were large steel shafts with a sharpened point. However, when inserting the trocar, a surgeon must exert considerable force on the proximal end so that the sharpened tip would provide a cutting and separating action at the same time. The force required to penetrate the body wall is related to the resistance of the tissue and muscle as well as the size and sharpness of the trocar tip. Often forcing the trocar through the body wall resulted in the trocar plunging through the body wall and injuring body organs or other tissue or vessels underneath.
2. Description of the Prior Art
Prior art trocars have been designed which provide a safety shield which plunges forward after penetration, covering the trocar tip and protecting the patient. These designs use a safety cover which is projected forward to cover the trocar's distal end or provide a mechanism for retracting the cutting tip while leaving the safety shield extended.
One example of a safety trocar is shown in U.S. Pat. No. 4,535,773 to Yoon. The trocar in this invention provides a safety shield which is spring loaded and which extends forward into the body cavity surrounding the point of the obturator when resistance of the tissue is removed. A trocar of this type requires the incision formed by the obturator to extend to a considerable diameter before the resistance of the tissue pressure has been sufficiently decreased to allow the safety shield to spring forward.
Another safety trocar of interest is shown in the patent to Moll (U.S. Pat. No. 4,601,710) which describes a trocar assembly consisting of two subassemblies, a sharp tipped trocar and a spring loaded tubular safety shield and a cannula subassembly. Initially the safety shield covers the trocar tip and exertion of pressure against the skin with the trocar causes the shield to be pushed rearwardly to expose the cutting tip. After the skin is penetrated through the wall, the force against the front end of the shield ceases and the shield automatically moves back to its distally extended position thereby protecting internal tissue from the sharp piercing tip.
The patent to Green (U.S. Pat. No. 5,116,353) describes a safety trocar whereby the cutting tip is withdrawn into a cannula in response to a counterforce being removed from the cutting tip when the tip enters a body cavity. The cutting tip is automatically withdrawn into the cannula under the force of a spring by means of a release mechanism which is actuated when resistance against penetration is lowered.
Still another patent of interest is to Deniega et al. (U.S. Pat. No. 5,215,526) which discloses a safety trocar including a spring loaded shield which covers the cutting tip of the obturator once it penetrates tissue. The distal end of the shield is hemispheric and contains a slot which conforms to the geometry of the cutting tip. The trocar also includes a valve at the proximal end to seal the end of the tube to prevent evacuation of gases from the body cavity.
In addition to the above, a number of prior art patents recognize the need for providing a seal at the proximal end of the trocar cannula structure to prevent venting of the body cavity. Another patent to Green (U.S. Pat. No. 5,129,885) provides a safety locking device for assuring proper matching relationship between a surgical instrument and a trocar guide tube or cannula housing.
The Shichman patent (U.S. Pat. No. 5,104,383) relates to a trocar seal for use with a cannula assembly for use with a variety of different sized instruments. The seal uses a stabilizer plate to limit the eccentric movement of the instrument to prevent inadvertent release of the seal.
The Stevens et al. patent (U.S. Pat. No. 5,197,955) relates to a trocar assembly which includes an improved seal to accommodate instruments having a wide range of diameters. A universal seal member is hourglass shaped and includes converging and diverging side walls forming a constricted center bore therebetween. Means are provided to increase or decrease the inner diameter of the center bore portion of the seal member to accommodate the various sized instruments.
The Ritchart et al. patent (U.S. Pat. No. 5,209,737) discloses a septum seal for a trocar assembly including an elastomeric septum disposed in a center channel. An assembly of levers pivot outwardly to expand or contract the seal to change the orifice opening to accommodate various sized instruments.
The Haindl patent (U.S. Pat. No. 4,917,668) discloses a valve for a cannula using a slotted valve body biased in a closed position by a metal spring.
The patent to Hilal et al. (U.S. Pat. No. 5,127,626) relates to an apparatus for sealing around a shaft including an elastomeric sealing body in a housing, a clamp and biasing arrangement to compress the sealing body into a sealed position.
Other patents of interest relating to trocars include, but are not limited to, the patent to Wescott (U.S. Pat. No. 1,380,447), Ekbladh et al. (U.S. Pat. No. 4,490,136), Reich et al. (U.S. Pat. No. 5,009,643), Lander (U.S. Pat. No. 5,030,206), Fleischhacker (U.S. Pat. No. 5,092,857) , Brinkerhoff et al. (U.S. Pat. No. 5,104,382), Castillenti (U.S. Pat. No. 5,147,316), Plyley et al. (U.S. Pat. No. 5,152,754), Borgia et al. (U.S. Pat. No. 5,158,552) , Allgood et al. (U.S. Pat. No. 5,176,651) , Shickman et al. (U.S. Pat. No. 5,217,441) and Freitas (U.S. Pat. No. 5,217,451) .